The present invention relates to optical reading devices in general and in particular to an apparatus for packaging illumination optical elements, receive optical elements, and signal processing elements of an optical reader.
Currently available optical readers include illumination elements, electronic signal processing circuits, image capture circuits and decoding circuits that are carried by more than one circuit board. For example, shown in U.S. Pat. No. 5,780,834 is an optical reader having numerous circuit boards, including an LED board for carrying illumination LEDs, an xe2x80x9cimaging boardxe2x80x9d carrying an image sensor and circuitry for processing signals generated from the image sensor, and a xe2x80x9cmother boardxe2x80x9d carrying image capture and decoding circuitry. U.S. Pat. No. 5,521,366 describes a modular housing having a rear printed circuit board, a front printed circuit board and a LED circuit board on which LEDs are mounted.
Assembly of a prior art reader requires mounting of separate circuit boards to separate internal structures of a reader, and providing electrical connection between the multiple circuit boards. In addition to being difficult to assemble, the multiple circuit board design imposes size requirements on the optical reader housing in which the electrical components are to be integrated.
There is a need for an easier to manufacture and lower cost packaging apparatus for packaging optical and electrical components of an optical reader.
According to its major aspects and broadly stated the present invention is a module for packaging optical illumination, optical receive, and electrical signal processing components of an optical reader.
The module includes a frame which carries a circuit board, preferably a printed circuit board (PCB) and various optical components. In one embodiment, the frame includes a back plate having a retainer for receiving an optical lens barrel, and a recess for receiving and aligning an image sensor which is carried by the PCB. The frame may also include resilient fingers which enable the frame to receive certain optical components of the module in an adhesiveless snap-fitting arrangement.
According to a preferred assembly method for assembling the module, the PCB is first mounted onto the frame""s back plate such that the image sensor of the PCB is received and aligned by the recess of the back plate. Next, illumination and aiming LEDs are soldered to the PCB to mount the LEDs. As a space conserving measure, the LEDs may be mounted so that a portion of rear surfaces of the illumination LEDs oppose a portion of the top surface of the image sensor when mounted.
After the LEDs are mounted to the PCB, additional components are incorporated in the module. In a preferred embodiment, a lens barrel is incorporated in the retainer, then an aperture plate having domed apertures for shaping light rays emanating from the aiming LEDs is placed over the LEDs. Finally, an optical plate for diffusing light rays emanating from the illumination LEDs is snap-fit into the frame. The optical plate may comprise discreet diffuser elements or may comprise a substantially uniform diffuser surface formed substantially over an entire surface thereof except for areas of the plate in which aiming optic elements are incorporated.
In addition to having diffusers for diffusing illumination light, the optical plate may also include optical elements for imaging light from the apertures onto a target defined by a reader""s field of view. In one embodiment of the invention, the aiming LEDs and their associated optics project a solitary horizontal aiming line onto a target in a field of view.
In another embodiment, the aiming LEDs and their associated optics project a split horizontal line aiming pattern onto a target in a field of view. The gap defined by the line segments of the split horizontal aiming line aid a user in locating the center of an optical reader""s field of view.
In another embodiment of the imaging module, the imaging module frame is deleted and the module retainer assembly is mounted to and supported entirely by the printed circuit board prior to being installed in a reader housing.
In another embodiment of the imaging module, the components of the imaging module are mounted on a xe2x80x9cflex stripxe2x80x9d type printed circuit board.
In another embodiment of the imaging module, light pipes are mounted to the printed circuit board. The light pipes transmit light from a source location proximate the circuit board to a location remote from the source location. The light pipes may be molded light pipes or may be provided by fiber optic cable.
In another embodiment of the imaging module, an image sensor is face-mounted to a printed circuit board, and folding optics are provided in the retainer assembly of the module for folding the optical imaging path so that the imaging path extends substantially parallel with the image sensor and circuit board. This type of module is especially well suited for installation in xe2x80x9cthinxe2x80x9d reader housings such as a reader housing for a personal data assistant or xe2x80x9cPDAxe2x80x9d device.
The printed circuit board may be a full function printed circuit board which carries a solid state image sensor and essentially the entirety of electronic circuitry required for supporting essentially all of the processing and control operations to be performed by the optical device in which the module is to be incorporated. Circuitry incorporated in the single PCB includes signal processing circuitry for processing signals generated from the image sensor, image capture circuitry for storing image data, and decoding and/or recognizing circuitry for decoding and/or recognizing indicia represented in image data that has been stored.
In order to accommodate the full function circuit board, the rear surface of the frame""s back plate should be made to have a central recess for aligning and receiving the image sensor, and peripheral recesses for accommodating circuit elements such as electrical components and/or wiring which may emanate from the front surface of the full function printed circuit board.
These and other details, advantages and benefits of the present invention will become apparent from the detailed description of the preferred embodiment herein below.